The present invention provides a simple and improved osmotic device that is capable of providing a controlled release of active agent contained in the core first through a preformed passageway and then through an in situ formed second passageway into an environment of use. One or both of the passageways optionally increases in size during use of the osmotic device. The preformed passageway and/or the second passageway increase the release rate of the active agent, enable the release of large particles containing active agent, and/or enable the release of active agents that are substantially insoluble in the environment of use. By virtue of the in situ formation of the second aperture, the device is able to release a greater overall percentage of active agent than it would release in absence of the second aperture.